1. Technical Field
The present invention relates to a sensor device, and to a measurement method.
2. Related Art
There are known sensor devices which, for example, measure the state of corrosion of a reinforcing bar in concrete (e.g., Japanese Laid-Open Patent Publication No. 11-153568).
Typically, the concrete in a concrete structure immediately after construction exhibits a strong alkalinity. For this reason, the reinforcing bars in a concrete structure immediately after construction have a passivation film formed on the surface thereof and are therefore safe. However, in a concrete structure that is affected after construction by acid rain, exhaust gas, and the like, the concrete will be gradually acidified, and the reinforcing bars will therefore corrode.
In view whereof, in, for example, the sensor device according to the above mentioned publication, fine wires composed of a material homogeneous to the reinforcing bars in the concrete structure are embedded in the concrete structure, and the corrosion state of the reinforcing bars in the concrete is predicted by the detection of the presence or absence of any fine wires disconnected by corrosion.
However, in the sensor device according to the above mentioned publication, between the time when the fine wires first begin to corrode and the time when a fine wire is disconnected, it is not possible to know the state of the reinforcing bars in the concrete structure nor of the concrete (more specifically, it is not possible to know, for example, the pH, or the concentration of chloride ions). Further, the reinforcing bars in the concrete structure corrode progressively between the time when the fine wires first begin to corrode and the time when a fine wire is disconnected. For this reason, entirely avoiding corrosion to the reinforcing bars in a concrete structure has not been a possibility, and this is a problem.